{	Problem: http://codeforces.ru/problemset/problem/103/A
	Verdict: Accepted
}
var
    n,i:longint;
   a:array[0..110] of int64;
    ans,cur:int64;

begin
read(n);
for i:=1 to n do
    read(a[i]);
ans := a[1];
for i:=2 to n do begin
    cur := 0;
    inc(cur,a[i]);
    inc(cur,(a[i] - 1) * (i - 1));
    inc(ans, cur);
end;
write(ans);
end.